1. Technical Field
The present invention relates to an organic electroluminescent device.
2. Related Art
An organic EL device including electroluminescent elements (hereinafter referred to as organic EL elements) is thought of as a display device including self-light-emitting elements not requiring a light source, such as a backlight.
A known organic EL device includes switching elements (for example, TFT elements) formed on a substrate, a planarizing layer reducing the unevenness resulting from the formation of the TFT elements, pixel electrodes formed on the planarizing layer corresponding to respective pixel regions and electrically connected to the TFT elements, a cathode, and an organic luminescent layer disposed between the pixel electrodes and the cathode. In this structure, the planarizing layer has contact holes through which the pixel electrodes and the TFT elements are electrically connected.
Japanese Unexamined Patent Application Publication No. 5-275172 discloses an organic EL device including a partition that prevents the pixel electrodes of adjacent pixel regions from coming into contact with each other or prevents the pixel electrode from coming into contact with the cathode. The partition is made of the same material as the planarizing layer, such as acrylic resin or polyimide.
In the manufacture of an organic EL devicer the pixel electrode, which may be made of ITO (indium tin oxide), is subjected to plasma treatment to clean the surface to remove soil before forming the organic luminescent layer on the pixel electrode.
However, plasma treatment partially etches the acrylic resin or polyimide of the partition and deposits foreign matter on the pixel electrode. Thus, the surface of the pixel electrode may be contaminated, and consequently the light-emitting characteristics are degraded.
Accordingly, in Japanese Unexamined Patent Application Publication No. 2005-216714, the organic material of the partition is improved to prevent the problems resulting from plasma treatment.
In order to favorably remove soil from the surface of the pixel electrode, high-intensity plasma treatment is desired.
However, the partition material disclosed in Japanese Unexamined Patent Application Publication No. 2005-216714 is an organic material, and organic materials have a limitation in resistance to plasma. Thus, the organic material of the partition does not have a sufficient resistance to plasma.
Accordingly, the plasma intensity is reduced, and consequently the surface of the pixel electrode cannot be sufficiently cleaned. On the contrary, the partition undergoes plasma treatment with exposure to plasma beyond the resistance, thus contaminating the surface of the pixel electrode. Consequently, the light-emitting characteristics of the organic EL device may be degraded.